Cross-linker monomer comprising double bond and photoresist copolymer containing the same

ABSTRACT

The present invention provides a cross-linker monomer of formula 1, a photoresist polymer derived from a monomer comprising the same, and a photoresist composition comprising the photoresist polymer. The cross-linking unit of the photoresist polymer can be hydrolyzed (or degraded or broken) by an acid generated from a photoacid generator on the exposed region. It is believed that this acid degradation of the cross-linking unit increases the contrast ratio between the exposed region and the unexposed region. The photoresist composition of the present invention has improved pattern profile, enhanced adhesiveness, excellent resolution, sensitivity, durability and reproducibility.                    
     where A, B, R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and k are as defined herein.

CROSS-REFERENCES TO RELATED APPLICATIONS

This is a Continuation-In-Part application of U.S. patent applicationSer. No. 09/643,460, filed Aug. 22, 2000, now U.S. Pat. No. 6,403,281which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to photoresist cross-linker monomerscomprising double bonds, photoresist polymers derived from the same andphotoresist compositions comprising such polymer. In particular, thepresent invention relates to acid labile photoresist cross-linkermonomers, polymers derived from the same, and photoresist compositionscomprising such polymer. The photoresist compositions of the presentinvention are suitable for photolithography processes employing KrF,ArF, EUV, VUV and similar light sources.

2. Description of the Background Art

Recently, chemical amplification-type DUV photoresists have beeninvestigated to increase sensitivity in minute image formation processesfor preparing semiconductor devices. Such photoresists are prepared byblending a photoacid generator and a matrix resin polymer (i.e.,photoresist polymer) comprising an acid labile group.

In a photolithography process, an exposure of photoresist to light of aparticular wavelength generates an acid from the photoacid generatorthat is present in the photoresist. This generated acid causes the mainchain or the branched chain of the resin to decompose or becomecross-linked. In addition, the acid removes the acid labile group whichis present in the polymer and changes the polarity of the photoresist inthe exposed region. This polarity change creates a solubility differencein a developing solution between the exposed portion and the unexposedportion, thereby allowing a pattern formation. The resolution of thepattern that is formed depends on the wavelength of the light—i.e., ingeneral, a shorter wavelength allows formation of more minute patterns.

In general, a useful photoresist (hereinafter, abbreviated as “PR”) hasa variety of desired characteristics, such as excellent etchingresistance, heat resistance and adhesiveness. In addition, a photoresistshould be easily developable in a commercially readily availabledeveloping solution, such as 2.38 wt % or 2.6 wt % aqueoustetramethylammonium hydroxide (TMAH) solution. However, it is verydifficult to synthesize a photoresist polymer that satisfies all ofthese characteristics.

A resin (i.e., photoresist polymer) like novolac resin having hightransparency and high etching resistance at 193 nm of wavelength hasbeen investigated. In addition, researchers at the Bell Research Centerhave investigated improving the etching resistance by increasing theamount of alicyclic units in the polymer backbone of the resin.Furthermore, Fujitsu and Sipri have studied the effect of addingmethacrylate and/or acrylate monomers to improve the etching resistance.Unfortunately, the resulting polymers do not have satisfactory etchingresistance. Moreover, the cost of producing polymers having increasedalicyclic units in the polymer backbone is significantly higher.Furthermore, many photoresist polymers generally have low adhesiveness;therefore, the dense L/S pattern below 150 nm may not form properly.

Therefore, there is a need for a photoresist monomer which provides apolymer having the above described characteristics.

SUMMARY OF THE INVENTION

The present inventors have found that the contrast ratio between theexposed region and the unexposed region of a photoresist film can beenhanced by adding a cross-linker monomer having, preferably, two doublebonds to the PR polymer. Moreover, it has been found that the additionof cross-linker monomer as a comonomer also improves a pattern profile.

Accordingly, an object of the present invention is to provide aphotoresist cross-linker monomer which comprises a double bond,preferably two double bonds. In particular, a cross-linker monomer whichcomprises an acid labile group.

Another objective of the present invention is to provide a photoresistpolymer derived from such photoresist cross-linker monomer. Preferably,the polymer has an excellent etching resistance, reproducibility,durability, adhesiveness and resolution.

Still another objective of the present is to provide a photoresistcomposition comprising such photoresist polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a photoresist pattern obtained in Example 5.

FIG. 2 shows a photoresist pattern obtained in Example 6.

FIG. 3 shows a photoresist pattern obtained in Example 7.

FIG. 4 shows a photoresist pattern obtained in Example 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a novel photoresist cross-linker monomer,which achieves the above stated objectives, and a process for producingthe same. The present invention also provides a photoresist polymerderived from the above described photoresist cross-linker monomer, and aphotoresist composition comprising such photoresist polymer. The presentinvention also provides a semiconductor device fabricated by using suchphotoresist composition.

The present invention provides a photoresist polymer comprising:

(i) two or more cycloolefin moieties, each comprising a carbon-carbondouble bond; and

(ii) at least one divalent group of the moiety

(where R is substituted or unsubstituted linear or branched alkylene)which is cleavable by an acid,

wherein the two or more cycloolefin moieties are connected by thedivalent group.

In one aspect of the present invention provides a photoresistcross-linker monomer of the formula:

wherein

each of A and B is independently cycloolefin;

each of R₁, R₂, R₃, R₄, R₅ and R₆ is independently H, or substituted orunsubstituted linear or branched (C₁-C₅) alkyl; and

k is an integer from 0 to 3.

Preferably, each of A and B is independently a moiety of the formula:

wherein

X₁ and X₂ individually represent CH₂, CH₂CH₂, O or S; n is an integerfrom 0 to 5; and R₇ and R8 individually represent hydrogen or methyl.

In one aspect of the present invention, the compound of formula 1 is,preferably of the formula

wherein R₁, R₂, R₃, R₄, R₅, R₆ and k are those defined above.

As shown in formula 2, the cross-linker monomer of the present inventionpreferably has two double bonds. As shown below, when a mixture of thecross-linker monomer and other photoresist comonomer(s) is polymerized,the cross-linker monomer of the present invention allow formation of across-linked polymer. Moreover, the cross-linker unit of thecross-linker monomer can be chemically degraded (i.e., broken) by theacid that is generated at the exposed region. This acid degradation ofthe cross-linker unit enhances the contrast ratio between the exposedregion and the unexposed region of the PR polymer.

Preferred photoresist polymers (i.e., copolymers) containing thecross-linker monomer of the present invention include polymer of theformula 3:

wherein R₁, R₂, R₃, R₄, R₅, R₆ and k are those defined above. Each of R₉and R₁₀ is independently H, or substituted or unsubstituted linear orbranched (C₁-C₅) alkyl; i is 0 or 1; m and n is independently an integerfrom 0 to 2; and the ratio of a:b:c:d:e=0-80 mol %:1-30 mol %:1-30 mol%:0.1-48 mol %:10-50 mol %.

It should be appreciated that the order of each monomeric unitsrepresented in a polymer formula of the present invention does notnecessarily indicate the actual order of such monomeric units in theactual polymer. The monomeric units represented in the polymer formulais simply intended to indicate the presence of such monomeric unit inthe polymer, i.e., when the variable a, b, c, d, or e is not 0.Moreover, the variables a, b, c, d, and e represents a total relativeratio of each units. For example, the total amount “e” of polymericunits derived from maleic anhydride may be inter dispersed throughoutthe polymer (not necessarily in same concentrations) or all or majorityof such polymeric unit may be concentrated in one particular location ofthe polymer.

As shown above, the cross-linker monomer of formula 1 can be polymerizedwith other photoresist comonomers using the originally present twodouble bonds. The resulting polymer is a cross-linked polymer due to thepresence of the polymeric unit derived from the cross-linker monomer.Moreover, the cross-linker monomers of the present invention comprisesester moieties which can be degraded (i.e., hydrolyzed) by an acid thatis generated from a photoacid generator at the exposed region. Withoutbeing bound by any theory, it is believed that this acid degradation ofthe polymeric unit derived from the cross-linker monomer of the presentinvention improves the contrast ratio between the exposed region and theunexposed region. Furthermore, unlike other photoresist monomers, e.g.,5-norbornene-2-tert-butylcarboxylate, photoresist cross-linker monomersof the present invention do not generate gas, e.g., isobutene.

As shown in formula 3, polymers of the present invention can comprise apolymeric unit derived from a monomer comprising a sterically bulkygroup. Accordingly, a predetermined amount of norbornylene andtetracyclododecene having a relatively small steric hindrance is addedto make it possible to properly control the molecular weight of thepolymer to about 5000 to about 8000, to increase the polymerizationyield to about 40% or more and to improve the thermal stability of thepolymer.

And, the etching speed of the photoresist is reduced relative to theconventional ultraviolet photoresist when the norbornylene and/or thetetracyclododecene moieties are present in the polymer. For example, ifthe etching speed of the ultraviolet photoresist using Cl₂ gas is “1”,the etching speed of polymers of the present invention comprising thenorbornylene and/or the tetracyclododecene moieties ranges from about0.8 to about 0.92.

The photoresist polymer of the present invention can be prepared by avariety of methods. In one particularly preferred method, polymers ofthe present invention are prepared by adding the cross-linker monomer offormula 1 to a mixture of other suitable photoresist monomer(s).

In one particular aspect of the present invention, the process forproducing a photoresist polymer of the present invention comprises thesteps of:

(a) admixing a cross-linker monomer of formula 1, at least one othersuitable photoresist monomer, and a polymerization initiator; and

(b) providing conditions sufficient to produce the photoresist polymer.

Preferably, the admixture is dissolved in an organic solvent prior tothe polymerization. While a variety of organic solvents can be used inpolymerization, the organic solvent is preferably selected from thegroup consisting of cyclohexanone, tetrahydrofuran, dimethylformamide,dimethylsulfoxide, dioxane, methylethylketone, benzene, toluene andxylene, and mixture thereof.

While a variety of reaction conditions afford the polymer from theadmixture, in one particular embodiment the polymerization conditionsinclude heating the admixture to temperature in the range of from about60 to about 70° C. for 4 to 24 hours under an inert atmosphere,preferably under a nitrogen or an argon atmosphere.

Advantageously, the polymerization initiator is selected from the groupconsisting of 2,2′-azobisisobutyronitrile (AIBN), acetylperoxide,laurylperoxide, tert-butyl peracetate, tert-butyl hydroperoxide anddi-tert-butylperoxide.

In addition, the process can further comprise crystallizing and/orpurifying the resulting polymer. In one particular embodiment,purification by crystallization can be achieved using a solvent selectedfrom the group consisting of diethyl ether; petroleum ether; alcoholincluding methanol, ethanol and isopropanol; water; and mixturesthereof.

The present invention also provides a photoresist composition comprisinga photoresist polymer of the present invention, an organic solvent and aphotoacid generator.

Sulfide or onium-type compounds are preferably used as the photoacidgenerator. Alternatively, suitable photoacid generators are selectedfrom the group consisting of diphenyl iodide hexafluorophosphate,diphenyl iodide hexafluoroarsenate, diphenyl iodidehexafluoroantimonate, diphenyl p-methoxyphenylsulfonium triflate,diphenyl p-toluenylsulfonium triflate, diphenylp-isobutylphenylsulfonium triflate, diphenyl p-tert-butylphenylsulfoniumtriflate, triphenylsulfonium hexafluororphosphate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium hexafluoroantimonate,triphenylsulfonium triflate and dibutylnaphthylsulfonium triflate.Preferably, the amount of photoacid generator is in the range of from0.05 to 10% by weight of the polymer employed. It has been found thatwhen the photoacid generator is used in the amount less than about0.05%, it lowers the photosensitivity of PR composition, and when thephotoacid generator is used in the amount greater than about 10%, itresults in a poor pattern formation presumably due to its high lightabsorption.

The organic solvent for photoresist composition is preferably selectedfrom the group consisting of methyl 3-methoxypropionate, ethyl3-ethoxypropionate, propylene glycol methyl ether acetate andcyclohexanone, cyclopentanone, 2-heptanone and (2-methoxy)ethyl acetate.The amount of solvent used is preferably in the range of from about 200%to about 1000% by weight of the PR resin (i.e., PR polymer). This ratiohas been found to be particularly useful in obtaining a photoresistlayer of desirable thickness when coated on to a suitable substrate suchas a silicon wafer in production of a semiconductor element. Inparticular, it has been found by the present inventors that when theamount of organic solvent is about 500% by weight of the PR polymer, aPR layer having 0.5 μm of thickness can be obtained.

In one aspect of the present invention, the photoresist composition isprepared by dissolving the polymer in an amount of 10 to 30% by weightof the organic solvent employed, blending the photoacid generator in anamount of 0.05 to 10% by weight of the polymer employed, and filteringthe resulting mixture with a hyperfine filter.

The present invention also provides a process for forming a photoresistpattern comprising the steps of:

(a) coating a photoresist composition described above on a substrate ofa semiconductor element to form a photoresist film;

(b) exposing the photoresist film to light using a light source; and

(c) developing the exposed photoresist film.

The process for forming the photoresist pattern can further include abaking step before and/or after the exposure step (b). Preferably, thebaking step is performed at temperature in the range of from about 70 toabout 200° C.

Exemplary light sources which are useful for forming the PR patterninclude ArF, KrF, EUW, VUV, E-beam, X-ray and ion beam. Preferably, theirradiation energy is in the range of from about 1 mJ/cm² to about 100mJ/cm².

The developing step (c) can be carried out using an alkali developingsolution or distilled water. The alkali developing solution ispreferably an aqueous solution comprising from about 0.01 to about 5 wt% of TMAH.

Furthermore, the present invention provides a semiconductor device,which is manufactured using the photoresist composition described above.

Additional objects, advantages, and novel features of this inventionwill become apparent to those skilled in the art upon examination of thefollowing examples thereof, which are not intended to be limiting.

I. Preparation of Polymer

EXAMPLE 1 Synthesis of poly(mono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate/maleicanhydride/norbornene/tert-butylbicyclo-[2.2.1]hept-5-ene-2-carboxylate/2,4-pentanediol-di-5-norbornene-2-carboxylate)

To 25 mL of tetrahydrofuran was addedmono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate (10 mmol), maleic anhydride(100 mmol), norbornene (33 mmol), tert-butylbicyclo-[2.2.1]hept-5-ene-2-carboxylate (55 mmol),2,4-pentanediol-di-5-norbornene-2-carboxylate (2 mmol) and AIBN (0.30g), and the resulting mixture was heated to about 65° C. for 8 hours.The polymer thus prepared was precipitated in diethyl ether or diethylether/petroleum ether mixture to produce a crude solid. The solid wasfiltered and dried to obtain the title polymer.

EXAMPLE 2 Synthesis of poly(mono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate/maleicanhydride/norbornene/tert-butylbicyclo-[2.2.1]hept-5-ene-2-carboxylate/1,5-pentanediol-di-5-nornornene-2-carboxylate)

The title polymer obtained by repeating the procedure of Example 1 butusing 1,5-pentanediol-di-5-nornornene-2-carboxylate (2 mmol) instead of2,4-pentanediol-di-5-nornornene-2-carboxylate (2 mmol).

EXAMPLE 3 Synthesis of poly(mono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate/maleicanhydride/norbornene/tert-butylbicyclo-[2.2.1]hept-5-ene-2-carboxylate/1,4-butanediol-di-5-nornornene-2-carboxylate)

The title polymer obtained by repeating the procedure of Example 1 butusing 1,4-butanediol-di-5-nornornene-2-carboxylate (2 mmol) instead of2,4-pentanediol-di-5-nornornene-2-carboxylate (2 mmol).

EXAMPLE 4 Synthesis of poly(mono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1 ]hept-5-ene-2,3-dicarboxylate/maleicanhydride/norbornene/tert-butylbicyclo-[2.2.1]hept-5-ene-2-carboxylate/1,3-butanediol-di-5-nornornene-2-carboxylate)

The title polymer obtained by repeating the procedure of Example 1 butusing 1,5-pentanediol-di-5-nornornene-2-carboxylate (2 mmol) instead of1,3-butanediol-di-5-nornornene-2-carboxylate (2 mmol).

II. Preparation of Photoresist Composition and Formation of Pattern

EXAMPLE 5

To 50 g of ethyl 3-ethoxypropionate was added 10 g of the polymerprepared in Example 1, and 0.12 g of triphenylsulfonium triflate as aphotoacid generator. The resulting mixture was stirred and filteredthrough a 0.20 μm filter to prepare a photoresist composition.

The photoresist composition thus prepared was spin-coated on a siliconwafer, and soft-baked in an oven or hot plate of 110° C. for 90 seconds.After baking, the photoresist was exposed to light using an ArF laserexposer, and then post-baked at 120° C. for 90 seconds. When thepost-baking was completed, it was developed in 2.38 wt % aqueous TMAH(tetramethylammonium hydroxide) solution for 40 seconds to obtain a 0.13μm L/S pattern (See FIG. 1).

EXAMPLE 6

To 50 g of ethyl 3-ethoxypropionate was added 10 g of the polymer 5prepared in Example 2, and 0.12 g of triphenylsulfonium triflate as aphotoacid generator.

The resulting mixture was stirred and filtered through a 0.20 μm filterto prepare a photoresist composition.

The photoresist composition thus prepared was spin-coated on a siliconwafer, and soft-baked in an oven or hot plate of 110° C. for 90 seconds.After baking, the photoresist was exposed to light using an ArF laserexposer, and then post-baked at 120° C. for 90 seconds. When thepost-baking was completed, it was developed in 2.38 wt % aqueous TMAH(tetramethylammonium hydroxide) solution for 40 seconds to obtain a 0.13μm L/S pattern (See FIG. 2).

EXAMPLE 7

To 45 g of ethyl 3-ethoxypropionate was added 10 g of the polymerprepared in Example 3, and 0.12 g of triphenylsulfonium triflate as aphotoacid generator.

The resulting mixture was stirred and filtered through a 0.20 μm filterto prepare a photoresist composition.

The photoresist composition thus prepared was spin-coated on a siliconwafer, and soft-baked in an oven or hot plate of 110° C. for 90 seconds.After baking, the photoresist was exposed to light using an ArF laserexposer, and then post-baked at 120° C. for 90 seconds. When thepost-baking was completed, it was developed in 2.38 wt % aqueous TMAH(tetramethylammonium hydroxide) solution for 40 seconds to obtain a 0.13μm L/S pattern (See FIG. 3).

EXAMPLE 8

To 45 g of ethyl 3-ethoxypropionate was added 10 g of the polymerprepared in Example 4, and 0.12 g of triphenylsulfonium triflate as aphotoacid generator.

The resulting mixture was stirred and filtered through a 0.20 μm filterto prepare a photoresist composition.

The photoresist composition thus prepared was spin-coated on a siliconwafer, and soft-baked in an oven or hot plate of 110° C. for 90 seconds.After baking, the photoresist was exposed to light using an ArF laserexposer, and then post-baked at 120° C. for 90 seconds. When thepost-baking was completed, it was developed in 2.38 wt % aqueous TMAH(tetramethylammonium hydroxide) solution for 40 seconds to obtain a 0.13μm L/S pattern (See FIG. 4).

As discussed above, photoresist polymers of the present inventioncomprise a polymeric unit derived from a cross-linker monomer. Thecross-linker monomer comprises functional moiety which can be degraded(e.g., broken or hydrolyzed) by an acid. As a result, the cross-linkerunit in polymers of the present invention can be hydrolyzed by the acidthat is generated in the exposed region. It is believed that this aciddegradation of the cross-linker is responsible for the increasedcontrast ratio between the exposed region and the unexposed region.Moreover, polymers of the present invention do not generate gases suchas isobutene, thereby restricting gas generation.

It has been found by the present inventors that photoresist compositionsof the present invention have improved pattern profile and enhancedadhesiveness, in addition to excellent resolution, sensitivity,durability and reproducibility.

What is claimed is:
 1. A photoresist polymer derived from a monomercomprising: (i) a cross-linker monomer of the formula:

wherein each of A and B is independently cycloolefin; each of R₁, R₂,R₃, R₄, R₅ and R₆ is independently H, or substituted or unsubstitutedlinear or branched (C₁-C₅) alkyl; and k is an integer from 0 to 3; and(ii) at least one other suitable photoresist monomer.
 2. The photoresistpolymer according to claim 1, wherein said A and B is independently amoiety of the formula:

wherein X₁ and X₂ individually represent CH₂, CH₂CH₂, O or S; n is aninteger from 0 to 5; and R₇ and R₈ individually represent hydrogen ormethyl.
 3. The photoresist polymer according to claim 1, wherein saidcross-linker monomer is the compound of the formula:


4. The photoresist polymer according to claim 1 of the formula:

wherein R₁, R₂, R₃, R₄, R₅, R₆ and k are those defined in claim 1; eachof R₉ and R,₁₀ is independently H, substituted or unsubstituted linearor branched (C₁-C₅) alkyl; i is 0 or 1; m and n is independently aninteger from 0 to 2; and the ratio of a:b:c:d:e=0-80 mol %:1-30 mol%:1-30 mol %:0.1-48 mol %:10-50 mol %.
 5. A process for preparing aphotoresist polymer of claim 1, comprising the steps of: (a) admixing(i) a cross-linker monomer of the formula:

wherein A, B, R₁, R₂, R₃, R₄, R₅, R₆ and k are those defined in claim 1;(ii) at least one other suitable photoresist monomer, and (iii) apolymerization initiator; and (b) providing polymerization conditionssufficient to produce said photoresist polymer from said admixture ofstep (a).
 6. The process according to claim 5, wherein saidpolymerization conditions comprises heating said admixture totemperature in the range of from about 60 to about 70° C. for 4 to 24hours under an inert atmosphere.
 7. The process according to claim 5,wherein said admixture further comprises an organic solvent selectedfrom the group consisting of cyclohexanone, tetrahydrofuran,dimethylformamide, dimethylsulfoxide, dioxane, methylethylketone,benzene, toluene, xylene and mixtures thereof.
 8. The process accordingto claim 5, wherein said polymerization initiator is selected from thegroup consisting of 2,2′-azobisisobutyronitrile (AIBN), acetylperoxide,laurylperoxide, tert-butyl peracetate, tert-butyl hydroperoxide anddi-tert-butylperoxide.
 9. The process according to claim 5, wherein saidprocess further comprises the step of purifying said polymer bycrystallization using a crystallization solvent selected from the groupconsisting of diethylether; petroleum ether; alcohol; water; andmixtures thereof.
 10. A photoresist composition comprising: (i) aphotoresist polymer of claim 1, (ii) an organic solvent and (iii) aphotoacid generator.
 11. The composition according to claim 10, whereinsaid photo acid generator is a sulfide or onium type compound.
 12. Thecomposition according to claim 10, wherein said photoacid generatorcomprises diphenyl iodide hexafluorophosphate, diphenyl iodidehexafluoroarsenate, diphenyl iodide hexafluoroantimonate, diphenylp-methoxyphenylsulfonium triflate, diphenyl p-toluenylsulfoniumtriflate, diphenyl p-isobutylphenylsulfonium triflate, diphenylp-ted-butylphenylsulfonium triflate, triphenylsulfoniumhexafluororphosphate, triphenylsulfonium hexafluoroarsenate,triphenylsulfonium hexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, or mixtures thereof.
 13. Thecomposition according to claim 10, wherein the amount of said photoacidgenerator is in the range of from about 0.05 to about 10% by weight ofsaid photoresist polymer.
 14. The composition according to claim 10,wherein said organic solvent is selected from the group consisting ofmethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propylene glycolmethyl ether acetate, cyclohexanone, cyclopentanone, 2-heptanone and(2-methoxy)ethyl acetate.
 15. The composition according to claim 10,wherein the amount of said organic solvent is in the range of from about200 to about 1000% by weight of said photoresist polymer.
 16. A processfor forming a photoresist pattern, comprising the steps of: (a) coatingsaid photoresist composition of claim 10 on a substrate of semiconductordevice to form a photoresist film; (b) exposing said photoresist film tolight using a light source; and (c) developing said exposed photoresistfilm.
 17. The process according to claim 16, further comprising: abaking step before and/or after exposure of step (b).
 18. The processaccording to claim 17, wherein the baking step is performed at 70 to200° C.
 19. The process according to claim 16, wherein said light sourceis ArE, KrF, VUV, EUV, E-beam, X-ray or ion beam.
 20. The processaccording to claim 16, wherein said photoresist film is irradiated withfrom about 1 mJ/cm² to about 100 mJ/cm² of light-exposure energy.
 21. Asemiconductor device manufactured by the process of claim
 16. 22. Aphotoresist polymer comprising: (i) a cross-linker monomer having: (a)two or more cycloolefin moieties, each comprising a carbon-carbon doublebond; and (b) at least one divalent group of the moiety

where R is substituted or unsubstituted linear or branched alkylene)which is cleavable by an acid, wherein the two or more cycloolefinmoieties are connected by the divalent group; and (ii) at least onesuitable photoresist monomer.
 23. The photoresist polymer of claim 22wherein said photoresist monomer is selected from the group consistingof mono-2-ethyl-2-(hydroxymethyl)butylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate, maleic anhydride, norborneneand tert-butyl bicyclo -[2.2.1]hept-5-ene-2-carboxylate.